The present invention relates to a power window apparatus, and more particularly, to a control to open and close a window glass.
In recent years, various motors have been mounted on vehicles to improve convenience. For example, a power window apparatus, which raises and lowers a window glass with a direct current (DC) motor, is mounted on many vehicles. In the power window apparatus, an operation switch is first operated by an operator, so that a motor electronic control unit (motor ECU), which is electrically connected to the operation switch, controls the motor according to an input signal from the operation switch. Torque produced by the motor is then transmitted to the window glass via a mechanical structure, to raise or lower the window glass.
In such a power window apparatus, a board on which the motor ECU is mounted (motor controller) may have a waterproof structure shown, for example, in Japanese Laid-Open Patent Publication No. 2002-13964, to prevent water entry when the vehicle is submerged in water.
In some power window apparatus, a board, on which an operation switch (switch unit) is mounted, and a motor controller are connected via a connector. In a power window apparatus where the connector is arranged on the board of the switch unit, however, the connected parts of the connector and the switch unit often do not have a waterproof structure. If this power window apparatus is submerged in water, water enters into the connected parts of the connector and the switch unit. Such water entry causes leakage current to flow between terminals of the connector. The leakage current may cause the motor ECU to incorrectly recognize its input signal. Particularly, when the motor ECU drives the motor to raise or lower the window glass in response to a low-level input signal (active-low control), the motor ECU may incorrectly recognize its input signal due to water entry.
FIG. 1 shows a conventional power window apparatus 50. The power window apparatus 50 includes a switch unit 52, which has an operation switch 51, and a motor controller 53. The switch unit 52 and the motor controller 53 are connected by a wire harness 54 via a connector (not shown). The operation switch 51 includes a lowering switch 55 and a raising switch 56. When, for example, the driver operates the operation switch 51 to lower a window glass, the lowering switch 55 is closed and a down terminal 57 is electrically connected to a ground terminal 58. This electrical connection causes the operation switch 51 to output an input signal V1 having a ground level (low-level) from the down terminal 57. A microcomputer 59 included in the motor controller 53 detects the state of the lowering switch 55 based on an input signal V1 provided via another down terminal 60. When the input signal V1 is at ground level, the motor controller 53 actuates a driver circuit 61 to drive a motor M. In this way, in the power window apparatus 50, the microcomputer 59 executes active-low control over the motor M. To maintain input signals V1 and V2 at a high-level when the operation switch 51 is not operated, a pull-up resistor R1 is connected between the down terminal 60 and a power supply V0, and a pull-up resistor R2 is connected between an up terminal 62 and the power supply Vo.
When the power window apparatus 50 is submerged in water, water enters into the connected parts of the connector and the switch unit 52. This may cause leakage current to flow between, for example, the down terminal 57 and the ground terminal 58 of the switch unit 52. The resistance of a leakage resistor RL10 between the two terminals is smaller than the resistance of the pull-up resistor R1. Therefore, the microcomputer 59 detects a low-level input signal V1 like when the lowering switch 55 is closed. This causes the microcomputer 59 to incorrectly recognize that the lowering switch 55 is in a closed state when the operation switch 51 is not operated.